In recent years, various flat-panel devices as typified by liquid crystal display devices have been put into practical use, and they are often provided in a variety of types of electronic equipment, including, for example, mobile electronic equipment such as cell phones. In particular, such mobile electronic equipment achieves further miniaturization by integrally, i.e., monolithically, forming display elements with part or all of its driver circuits on a polysilicon device substrate.
The configuration of a liquid crystal panel, which is a liquid crystal display device having display elements and driver circuits monolithically formed on a substrate as mentioned above, will be described with reference to FIGS. 4 and 5.
FIG. 4 is an external perspective view of a conventional liquid crystal panel. As shown in FIG. 4, this liquid crystal panel 900 is formed by providing a liquid crystal layer between an element-side substrate 901 and an opposing-side substrate 902, and these substrates are attached via a predetermined seal material in which the liquid crystal layer is enclosed.
Furthermore, the element-side substrate 901, which is a device substrate, has formed thereon an element array area 905 consisting of display elements arranged in a matrix, each element being made up of pixel circuits which include thin-film transistors (TFTs), and driver circuits for driving the display elements, including, for example, agate driver to be described later, are formed around the element array area 905.
Note that, in actuality, the element-side substrate 901 has provided on its surface opposite to the opposing-side substrate 902 a backlight unit for radiating light in the direction toward the opposing-side substrate 902 or a reflective plate for reflecting outside light in the same direction, and the transmittance of the light is changed to a desired value by appropriately controlling the voltage applied to the liquid crystal (specifically, the voltage between pixel electrodes provided for their respective display elements and a common electrode on the opposing-side substrate 902 provided commonly for the display elements), so that display is provided at adesired tone in the direction toward the opposing-side substrate 902.
Furthermore, the element-side substrate 901 is connected to an FPC (flexible printed circuit) substrate 904 to which video signals are transmitted from outside the liquid crystal panel 900, and the video signals are supplied through the FPC substrate 904 to a source driver IC 903 provided on the element-side substrate 901. The source driver IC 903 provides the video signals to the display elements within the element array area 910. A further detailed circuit configuration of the element-side substrate 901 will be described.
FIG. 5 is a plan view illustrating a circuit configuration of the conventional element-side substrate having part of its driver circuits monolithically formed with display elements. As shown in FIG. 5, the element-side substrate 901 has a plurality of display elements arranged in a matrix within the aforementioned element array area 905, the display elements display red (R), green (G), or blue (B), and each group (unit) of three display elements for displaying these three colors forms a single color pixel. In the figure, for example, a display element 951 displays red, and a single color pixel is formed by three adjacent display elements arranged in the row direction. The display elements are provided near intersections of a plurality of source lines provided in parallel in the column direction (here, the vertical direction of the screen) and a plurality of gate lines provided in parallel in the row direction (here, the horizontal direction of the screen), and video signals provided from the source lines are received and held by (TFTs included in) display elements activated at predetermined times by scanning signals from a gate driver 911, which is a row control circuit monolithically formed within the element-side substrate 901. These features are well-known, and therefore, any detailed descriptions thereof will be omitted.
Furthermore, the element-side substrate 901 has monolithically formed thereon an RGB switch circuit 912, which consists of a plurality of sampling units, including a sampling unit 9121, for sequentially switching source lines coupled to the display elements for displaying the three colors, and control circuits 913a and 913b provided on opposite ends of the circuit, including various signal protection element units, buffer circuits, level shifter circuits, and so on. In addition, provided outside a sealed area 906 of the element-side substrate 901 are a plurality of control signal terminals 940 for connection with the FPC substrate 904, the source driver IC 903 included in the aforementioned driver circuits (as a part), and input signal terminals 941 to the source driver IC 903.
The conventional liquid crystal panel is configured to receive well-known control signals (e.g., clock pulses, start pulses, etc.) from an unillustrated external display control circuit, and concretely, these control signals are provided to the RGB switch circuit 912 and the gate driver 911 via the control signal terminals 940. Note that the control circuits 913a and 913b are supplied with power from an unillustrated power supply circuit via power lines.
Furthermore, to provide a predetermined common potential to the common electrode of the opposing-side substrate 902, four common transfer electrodes 907 are provided on the element-side substrate 901. The common transfer electrodes 907 are electrically connected to the common electrode via conductive particles or suchlike contained in a conductive paste or a seal material. The common transfer electrodes 907 are connected to the control signal terminals 940 via wiring, and are externally provided with the predetermined common potential.
Here, since the number of lines for providing video signals from the source driver IC 903 to the RGB switch circuit 912 is significant (typically, several hundred), and the long side (horizontal or column-wise) of the RGB switch circuit 912 is normally longer than the long side of the source driver IC 903, these lines are provided so as to spread like a fan from the source driver IC 903 to the RGB switch circuit 912. In such a case, the distance “h” between the source driver IC 903 and the RGB switch circuit 912 needs to be somewhat long, even if wiring intervals (pitches) are minimized within design tolerance.
However, as the distance “h” increases, a frame region around the element array area 905 widens. The frame region does not contribute to display and therefore is desirably small, and furthermore, it is desirably as small as possible to miniaturize the liquid crystal display device.
Therefore, conventional liquid crystal display devices are configured, for example, such that, where a plurality of source drivers IC are provided, the number of output terminals (the number of lines) thereof is set to a divisor of the total number of signal lines without leaving a remainder (see Japanese Laid-Open Patent Publication No. 11-338438), and the number of control signals to be provided to the RGB switch circuit is reduced (see Japanese Laid-Open Patent Publication No. 2008-76443), and such configurations can reduce the frame region.